1. Field of the Invention
The invention relates to an electronic still camera and to an image pickup apparatus and a solid state image pickup device which are suitable for use in an electronic still camera.
2. Description of the Related Art
Recently, the electronic still camera is being spread. As a solid state image pickup device, for example, a CCD which is suitable for use in the electronic still camera, a device of a square lattice and a device of a progressive scan have been proposed. According to the square lattice, an interval in the vertical direction of adjacent pixels and an interval in the lateral direction are equalized and it is used to match an image pickup signal with a signal for a monitor for a personal computer. According to a CCD which is used in a conventional video camera or the like, in order to generate an output signal of an interlace type, as shown in FIG. 28, charges are accumulated for {fraction (1/60)} second (one field), the charges of pixels of upper and lower two adjacent lines are read out, the charges of the two pixels which were read out are mixed in a CCD for vertical transfer, a combination in the vertical direction of the two pixels to be mixed is deviated with respect to an odd field and an even field, thereby realizing an interlace scan.
According to such a CCD, since an accumulating time is equal to {fraction (1/60)} second, as compared with a frame accumulation type of an accumulating time of {fraction (1/30)} second, an image pickup of a motion image can be preferably performed but there is a disadvantage such that a vertical resolution is low. Therefore, such a CCD is not suitable as an image pickup device of the electronic still camera. As shown in FIG. 29, therefore, a progressive scan system in which charges are accumulated for {fraction (1/30)} second and the charges of all pixels are independently read out without mixing has been proposed. According to such a system, although the deterioration in vertical resolution can be prevented, in order to output an image pickup signal from the image pickup device, a time that is twice as long as that of the image pickup device for the video camera mentioned above is needed on the assumption that the number of pixels is the same and a clock for reading out is the same. More specifically speaking, an image pickup signal at a period of {fraction (1/30)} second is generated.
In case of the electronic still camera, in order to focus at the time of photographing or adjust an angle of the camera upon photographing, a monitor to display a pickup image, for example, a liquid crystal monitor is frequently provided. The liquid crystal monitor usually displays a television image by a non-interlace scan of {fraction (1/60)} second. Therefore, when the image pickup signal at a period of {fraction (1/30)} second is supplied as it is to the liquid crystal monitor, an image as shown in FIG. 30 is derived. To avoid such a phenomenon, as shown in FIG. 31, for a liquid crystal monitor 62, it is necessary to convert a frame rate by a VRAM (video RAM) 61 (or frame memory). An image pickup signal at a period of {fraction (1/30)} second is supplied to the VRAM 61 and a non-interlace signal at a period of {fraction (1/60)} second is generated as an output.
As mentioned above, the image pickup device of the progressive scan type is suitable as an image pickup device of the electronic still camera with respect to a point that the vertical resolution is high. However, since the frame rate is changed in order to display the image pickup image to an ordinary television monitor, there is a problem such that a VRAM or a frame memory is necessary and the costs rise. Further, since the electronic still camera has automatic control apparatuses such as auto focus control apparatus, automatic iris control apparatus, auto white balance control apparatus, and the like, there occurs a problem such that since a period of an output signal of the image pickup device is long, a response speed of the automatic control is made slow. Further, there is also a problem such that a motion of an image which is displayed on the monitor is not smooth.
As a method of solving the foregoing problems, a data rate of the output signal of the image pickup device is raised. When a clock frequency is high, however, problems such as increase in electric power consumption, increase in costs of parts which are used, deterioration in S/N ratio, and the like occur. Therefore, the method of raising the data rate of the image pickup signal is unpreferable.
It is, therefore, an object of the invention to provide an image pickup apparatus which can output an image pickup signal at a high speed without losing an advantage such that a vertical resolution is high, thereby making a VRAM unnecessary.
Another object of the invention is to provide an image pickup apparatus in which when a pickup image is recorded to a recording medium or when data is read out from the recording medium, a period during which a display of a monitor disappears can be minimized.
Still another object of the invention is to provide a solid state image pickup device which can output an image pickup signal at a high speed.
According to an embodiment of the invention, the above objects are accomplished by an image pickup apparatus comprising:
a solid state image pickup device which can operate in a first image pickup mode for performing a reading operation of pixels of a first number of lines at a first period and a second image pickup mode for performing a reading operation of pixels of a number of lines smaller than the first number of lines at a second period different from the first period;
image signal forming means for forming an image signal from an output signal of the solid state image pickup device;
display means which can display an image signal at a period concerning the second period;
storing means for storing the image signal;
switching means for switching a connecting relation among the image signal forming means, the display means, and the storing means so as to enable a transfer of the image signal between any two of the image signal forming means, the display means, and the storing means; and
control means for setting a first recording mode to control so that the solid state image pickup device operates in the first image pickup mode and to control the switching means so as to connect the image signal forming means and the storing means when the image signal is stored into the memory means, and, for immediately shifting to a second recording mode to control so that the solid state image pickup device operates in the second operating mode and to control the switching means so as to connect the image signal forming means and the display means when the image signal is stored into the storing means in the first recording mode.
According to another embodiment of the invention, there is also provided an image pickup apparatus comprising:
a solid state image pickup device which can operate in a first image pickup mode for performing a reading operation of pixels of a first number of lines at a first period and a second image pickup mode for performing a reading operation of pixels of a number of lines smaller than the first number of lines at a second period different from the first period;
image signal forming means for forming an image signal from an output signal of the solid state image pickup device;
storing means for storing the image signal;
a coupling terminal which is connected to display means which can display an image signal at a period concerning the second period;
switching means for switching a connecting relation among the image signal forming means, the coupling terminal, and the storing means so as to enable a transfer of the image signal between any two of the image signal forming means, the coupling terminal, and the storing means; and
control means for setting a first recording mode to control so that the solid state image pickup device operates in the first image pickup mode and to control the switching means so as to connect the image signal forming means and the storing means when the image signal is stored into the memory means, and, for immediately shifting to a second recording mode to control so that the solid state image pickup device operates in the second operating mode and to control the switching means so as to connect the image signal forming means and the coupling terminal when the image signal is stored into the storing means in the first recording mode.
According to another embodiment of the invention, there is also provided a solid state image pickup device of an interline system, comprising:
a plurality of photosensors which are arranged in a matrix form and into which the lights transmitted through a plurality of color filters which are repeated in the vertical direction at a period of N (N is a natural number) pixels are inputted;
a vertical transfer unit for transferring charges read out from the plurality of photosensors without mixing charges from the photosensors continuously arranged in the vertical direction;
a horizontal transfer unit, coupled to the vertical transfer unit, for generating the charges transferred from the vertical transfer unit at one horizontal period;
a first signal supplying unit in which one unit is constructed by m (m is a natural number) first photosensor groups which are continuously arranged in the vertical direction and second photosensor groups of the number that is a (a is a natural number) times as large as the pixel period N which are continuously arranged in the vertical direction, the first photosensor groups and the second photosensor groups are alternately arranged in the vertical direction, and which is used for transferring the charges accumulated in the first photosensor groups to the vertical transfer unit; and
a second signal supplying unit for transferring the charges accumulated in the second photosensor groups to the vertical transfer unit,
wherein the first signal supplying unit and the second signal supplying unit are independently provided.
The above and other objects and features of the present invention will become apparent from the following detailed description and the appended claims with reference to the accompanying drawings.